1. Field of the Invention
This invention relates to docking facilities for vessels, and more particularly, to a moorage device for securing a line carried by a vessel to a pile at a location on the pile which is horizontally fixed yet moves vertically with vertical movement of the vessel responsive to tidal action.
2. Description of the Prior Art
Floating moorage is commonly used in marinas throughout the United States. Such moorage utilizes a relatively wide mainwalk float projecting outwardly from the shore and a large number of relatively narrow finger floats of varying lengths projecting perpendicularly from the mainwalk float at spaced-apart locations. This commonly used mooring arrangement works very well for fairly small boats, but tidal surges often cause damage to floats when longer finger floats required by larger boats are used. The tidal action in most West Coast ports is not smooth or slowly varying. Instead, tidal surges; i.e., waves or water level variations, are generally produced which may have an amplitude of between one and six feet. The larger size of the finger floats required for the larger boats often causes the vertical movement of the larger boats to lose synchronization with the vertical movement of the mainwalkway floats. Under these circumstances, the larger boats move upwardly on the surge when the floating mainwalk piers are moving downwardly. This action causes the boat to collide into the mainwalk and finger floats often with sufficient force to cause severe damage to boeth the vessel and float. The more serious surges frequently occur during the winter months at times when moored vessels are often unattended. Consequently, widespread damage often occurs before it is discovered.
The surge problem has, in many cases, prevented the use of the above-described floating moorage for larger vessels. Instead, a single floating mainwalk is used and a larger number of spaced-apart piles or groups of piles known as "dolphins" are driven into the sea bed along a line spaced from the edge of the mainwalk a distance approximately equal to the length of the vessels. The use of extra pile or dolphins cannot solve the surge problem and sometimes produce other problems as a result from a combination of surge plus tidal and wave action. It is desirable to prevent moored vessels from moving either transversely or longitudinally so that the vessel does not strike either the piles or the mainwalk. Consequently, lines extending between the vessel and the piles should be taut. However, taut lines extending around the piles often bind on the piles so that the lines are not able to move vertically along the pile as the vessel moves vertically responsive to tidal action. This results in extreme forces exerted on the pile by the boat which are frequently of sufficient magnitude to dislodge the pile from the sea floor. The vessel can then drift about with the pile, potentially causing a great deal of damage. Use of mainwalk and pile moorage thus presents the vessel operator with two options, neither of which is entirely satisfactory. The mooring lines can be left loose, in which case the vessel is free to move longitudinally or transversely to strike the mainwalk or piles; or the mooring line can be made taut, thereby risking removal of the pile from the sea floor.
Floating tie-up buoys have been developed and used commercially. However, these buoys are generally either floats which are loosely anchored to the sea floor and thus do not restrict boat movement or they are cylindrical floats loosely positioned in vertical slots formed along the walls of locks. Neither of these existing float structures are satisfactory for use with a pile or dolphin to allow a vessel to be securely moored at a pile and yet respond to tidal changes. A structure attempting to solve the above-described problems is shown in Standard Handbook of Civil Engineers, Frederick S. Merritt, page 23-61. One such attempt includes a rod extending vertically along the side of a pile. A mooring ring loosely surrounds the rod for free vertical movement. This structure does not employ a float nor is it strong enough for extreme weather particularly where the rod must be long enough to accommodate the large tides ranges frequently found in many areas.